Hot plate welding system

ABSTRACT

The invention disclosed hereunder is a process and a device for the preparation and formation of a plastic weld connection between a workpiece ( 13 ) and a second component to be attached thereto by heating by means of a heating device ( 12 ). If force is applied, the heating element ( 12 ) tends to deform the contact surface especially in the case of hollow, thin-walled workpieces such as plastic containers. So far, methods were disclosed for the measuring of the degree of deformation by means of a sensor, subsequently readjusting the position of the heating device according to the determined deformation. The invention disclosed here under dispenses with any measurement of deformation, instead using an elastic element which automatically readjusts the position of the heating element ( 12 ) in the case of deformation of the workpiece ( 13 ) to effect a pre-load between the heating device ( 12 ) positioned at the contact surface of the work-piece ( 13 ) and the workpiece ( 13 ).

SCOPE OF THE INVENTION

The present invention relates to a method and apparatus used to prepareand form weld connections between thin walled articles which may inthemselves be subject to distortion or deformation when subjected tocritical pressures or loading. The method more preferably involves thesoftening of the contact surface of the workpiece by means of a heatapplying application device which is moved into engagement with thecontact surface of the workpiece.

BACKGROUND OF THE INVENTION

When two components are connected by means of bonding, gluing orwelding, the elasticity of the components, namely their ability to bendor yield to pressure, often constitutes a significant problem in termsof the quality of the connection. The quality and integrity of theconnection can be reduced, particularly in the case of extrusion-blownhollow plastic bodies, due to the inconstant positioning of one of thecomponents during the melting and pressing process. Leaky weldconnections can lead to serious consequences in the context ofapplications where weld connections of a high quality are required, asfor example in the manufacture of plastic fuel tanks which require hightolerance limits as far as the location of the connecting surfaces isconcerned. In the context of such applications, the compensation oftolerance limits for the positioning of the contact surfaces with helpof a welding system is required.

German Patent No. DE 35 37 670 C2 to Oxenfarth, which issued on Mar. 3,1988, discloses a conventional process and corresponding device for usein forming a plastic weld connection. A minimum-force sensormechanically determines the position of the contact surface on aworkpiece such as a hollow plastic container (e.g. a fuel tank of avehicle). Once the workpiece position is determined, a welding head orother heat applying device is moved by the sensed distance into contactwith the workpiece to soften and melt a portion to which a secondcomponent is to be welded. This process assures safe welding of thesecond component, which for example may be a vent connection or fillerneck onto the workpiece in spite of high tolerance limits as far as thedimensions of the workpiece are concerned. Therefore, the use of thickermaterials to ensure complete welds, and which is almost impossible inthe case of thin-walled hollow bodies, is not required to effect theconnection. This procedure, however, neglects the forces that meltinghead apply to the workpiece and which can cause distortion or bending ofworkpiece surfaces, leading to incomplete welds.

DE-PS 39 22 066 discloses a further development of the state of the artused to achieve improved welds. This reference discloses a method tocompensate for position changes and deformation of the part of aworkpiece to which a second component is to be connected by readjustingthe position and contact pressure of a heating element, as well as theposition and contact pressure of the second component to be connected tothe workpiece. For this purpose, the position of the contact surface onthe workpiece is also determined by a minimum-force mechanical sensor.The result of the measuring process is then used to readjust a pistonwhich presses the component to be added against the heating device andthe heating device against the workpiece.

Published Japanese Patent Abstract No. 04 234633 to Yokoyama Takahito(published Aug. 24, 1992) discloses a holder used to position apolyethylene joint on a tank, following melting and heating of contactsurfaces. The holder includes a compression spring used to bias a meltedsurface of the joint against a melted surface of the tank.

Published Japanese Patent Abstract No. 08 112861 to Imagawa Kanji(published May 7, 1996) discloses a heating device used to heat weldtogether two sheets. The heating device includes a heating part which isbiased by means of a spring to project downwardly through an opening,into contact with the sheets which are to be welded.

The determination of the position of the workpiece surface using anadditional sensing device constitutes a disadvantage in that it is notsufficiently accurate, as the method requires the establishment ofadditional reference surfaces on a potentially elastically deformablesurface of the workpiece or component. In addition, the referencesurfaces are often not feasible for manufacturing related reasons, orare located too far from the relevant connecting position, thusdistorting the result.

Plastic welding units that are exclusively equipped with load-sensitivesensors such as load cells can compensate for the disadvantages ofexternal sensing equipment but are often expensive and are notsufficiently sensitive for design-related reasons. Additionally, theimpression depth achieved by the partial melting of the component orworkpiece surface is not adequately determined.

SUMMARY OF THE INVENTION

The invention is therefore based on the need to develop an improveddevice and a process for the formation of weld connections of constantquality as between a workpiece and a second component which is to beconnected thereto. More preferably, the present invention seeks toachieve the formation of high quality plastic weld connections whereeither the workpiece and/or the component may be elastically deformableupon the application of a predetermined minimum force thereto.

The inventor has appreciated an improved method of forming a plasticweld connection between a workpiece which can be shaped or deformed byapplication of mechanical force and a second component to be connectedthereto. The method preferably involves the softening of the contactsurface of the workpiece by application of heat, however, other means ofjoining components to the workpiece, such as gluing, sonic welding orthe like are also possible. The process broadly comprises the steps ofpositioning of an application device adapted to melt, glue or weld thecontact surface of the workpiece, activating the application device toprepare the contact portion of the workpiece while repositioning of theapplication device in relation to the workpiece during preparation ofthe contact portion. The method is further characterized by the factthat the repositioning comprises a defined displacement of theapplication device in relation to the contact surface of the workpiece,and which is independent of a determination of the position by means ofmeasuring.

The present invention also overcomes the disadvantages of the prior artby providing a device for the preparation and formation of a weldconnection between a workpiece which can be distorted or deformed uponthe application of predetermined mechanical force and a second componentwhich is to be connected thereto. The apparatus preferably includes ahot plate used in the softening or partial melting of the contactsurface of the workpiece when applied thereto. The apparatus ischaracterized by the fact that it is adapted to reposition the hot plateduring melting without measuring of the position of the contact surface,and most preferably during displacement of the hot plate while it isapplied to the contact surface of the workpiece as deformation andmelting of the contact surface occurs.

The invention preferably relates to a process for the preparation andformation of a plastic weld connection between a deformablethermoplastic workpiece which may be distorted by the application of amechanical force and a second thermoplastic component to be connectedthereto. In a preferred embodiment, the method includes a step ofsoftening or partial melting of the contact surface of the workpiece byapplication of heat. More preferably, the process includes the followingsteps: positioning a heat applying device at the contact surface,activating the heat applying device, and continuously repositioning theheat applying device in relation to the workpiece during the softeningof the workpiece.

Additionally, the present invention relates generally to a plasticwelding device for the preparation and formation of a weld connectionbetween a workpiece and a second component to be connected thereto.

The process and the device disclosed hereafter ensure that the loadforces of the element used in preparing or performing the weldingprocess is directly applied to the elastic component to be connected tothe workpiece, and applies a defined load and maintains a defined pathduring welding operations.

The basic principle of the present invention and process disclosed alsocompensates for different degrees of bending or flexure due toproduction-related differences in workpiece wall thickness, aging orvariations in material quality. Basically, the principle of the devicedisclosed hereunder is suitable for all processes where a workpiecehaving an elastically deformable surface must be prepared underpath-dependent and load-dependent conditions.

The preferred field of application, however, is for use in formation ofplastic weld connections where the contact surfaces of the twocomponents to be joined are softened by heating and pressed together ina defined fashion while still soft and partially melted. The pressingphase is followed by a cooling phase that allows the softened materialto harden to form a finished weld. By way of non-limiting examples, thepresent invention may be used to weld components such as thermoplasticvent nipples, filler necks or the like to blow moulded thermoplasticworkpieces, such as automotive gas tanks, fluid reservoirs or any otherplastic parts which may require welding.

According to the present invention, a pneumatically, hydraulically orelectrically operated advancing system is preferably used to press aheating element, which is controlled via a load-sensitive elementattached to the advancing device into contact with a partially elasticcontact surface. The mobility of the load-sensitive element shouldpreferably be limited to a translational one-dimensional motion. withthe preferred design allowing for adjustment of an admissible maximumpath. More preferably, the heating element is also equipped with aload-sensitive sensor.

Through the load-sensitive sensor, the heating element can be pressedonto the elastic contact surface until a predefined load value isreached. As soon as the predefined contact pressure is reached, theload-sensitive sensor operates to cease operation of the advancingsystem and the further movement of the heating element.

To achieve production-related even and homogeneous softening in the areaof the contact surface, the heating element is preferably advanced aminimum impression depth into the melting material at the contactsurface. The minimum impression depth of the heating element beingdefined as the maximum local shape or thickness at the contact surfaceand position tolerance required to compensate for any irregularities ofthe contact surface.

The predefined distance of movement of the load-sensitive elementdetermines the impression depth. As soon as the maximum impression depthis reached, the heating element engages the contact surface without anyfurther force being applied so as to ensure sufficient radiation andpenetration of heat and, thus a sufficient amount of softened materialfor the subsequent connecting process. Depending on the requirements ofthe application, the maximum impression depth can be monitored by asignal transmitter.

The load-sensitive mechanism ensures that reproducible impression depthand heating of the contact surface are achieved by simple mechanism,regardless of the elastic bending of the contact surface. An accuraterelation between the heating element and the contact surface is given atany moment, as the heating element directly performs the function of aposition sensor. The system disclosed hereunder is free of thedisadvantages which are characteristic of systems that use positionsensors and reference surfaces which, for production-related reasons,must be located at a certain distance from the contact surface.

The process disclosed hereunder does not in principle require thecontact surface to be additionally pre-loaded or biased against theheating element. This may be done, however, for economic reasons,because higher contact pressures applied to compensate forirregularities, while the heating element advances into the material,allow a significant reduction of production cycle times.

The load-sensitive sensor should preferably be an adjustable device,thus ensuring that the contact pressure required for differentproduction processes and workpieces can be defined. The load-sensitivesensor may also be designed in the form of a load cell, thus ensuringthat the documentation and recordal of the load parameters during theprocess is possible.

Depending on the counter forces originating from the deformation of thecontact surface, the load-sensitive element can be provided with a pathlimitation feature such as a stop. Thus it is possible to ensure thatthe heating element advances into the material exerting a relativelygreat force and within a correspondingly short time. As the contactsurface approaches the path limitation point, the external forcesdecrease towards zero and the heat can penetrate from the heatingelement into the material, substantially without any further forcesbeing applied. In contrast to other prior art hot welding systems, it isnot necessary to remove the load of the heating element from thedeformed contact surface during the heating process.

The separate pressing or advancing mechanism required to connect thecomponents to each other can be designed as desired, however,pneumatically, hydraulically or electrically operated systems arepreferred and will become readily apparent.

Although not essential, the softening of the component to be attached tothe workpiece should preferably be affected by means of the same heatingelement used to soften the elastic workpiece proper, using the surfaceof the heating element opposite from the elastic workpiece.

Path limitation and load measuring systems can be used to compensate fortolerances regarding the contact surfaces or for irregularities of thecomponent to be attached to the original workpiece. Considering the factthat the system disclosed hereafter can also be used for components withdeflection-resistant surfaces, it is recommended to use a load-sensitivemechanism according to the present invention to support the component tobe attached to the workpiece.

The present invention compensates for manufacturing irregularities andheight tolerances in the area of the contact surface, at the same timeensuring that the heating element advances to sufficiently deep levelinto an irregular contact surface, without requiring external pathmeasuring or continuous control devices and without additional referencesurfaces in the vicinity of the elastic contact surface.

In a process for the preparation or heating of an elastic contactsurface, heating, is effected by a heating element that is connected toan advancing mechanism via a sensing element. The advancing mechanismpreferably consists of a self-locking threaded spindle with an adequatedriving mechanism.

A particular advantage of the present invention resides in the fact thatthe adjustment of the loads exerted during the warming and the heatdiffusion stage, the registration of the location of the elastic contactsurface, and the determination as well as the limitation of the pathtraveled by the heating element during the warming stage can be effectedby one single device. Additionally, this device performs all requiredmovements.

Accordingly, in one aspect the present invention resides in a device forthe preparation and formation of a weld connection between a workpieceand a second component to be connected thereto, and including means forthe softening of the contact surface of the workpiece by applying anapplication device to the contact surface of the workpiece,characterized in that

the device includes means for repositioning the application devicewithout measuring of the position of the contact surface, and means fordisplacing the application device applied to the contact surface of theworkpiece in relation to the workpiece as soon as deformation of thecontact surface occurs.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference may now be had to the following detailed description takentogether with the accompanying drawings in which:

FIG. 1: is a side view of a first embodiment of the present invention;

FIG. 2 is a side view of a modified form of the invention of FIG. 1.

FIG. 3 is a side view of a second embodiment of the present invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The device shown in FIG. 1 comprises a base unit 1. Two articulatingarms or rods 2 and 3 are pivotally attached at one end to base unit 1,with the other ends of the arms 2,3 articulated with an adapter plate 7,and the arms 2,3 together forming a parallelogram. Due to this design,the adapter plate 7 can practically move in only one direction (in FIG.1 along the vertical axis). The second (horizontal) component ofmovement present in this system is insignificantly small, provided thatthe components are arranged accordingly, and can thus be neglected. Itis to be appreciated, however, that instead of arranging the two arms2,3 to form a parallelogram, it would also be possible to attach theadapter plate 7 to only one arm that glides up and down in a guidingdevice on the base unit 1. This design requires a greater effort tomount the arm in a guiding device on the base unit 1 but offers theadvantage of more complete elimination of the horizontal component ofmovement.

The base unit 1 comprises two fork-like extensions 21 and 22 betweenwhich the arms 2 and 3 are located. A spring 5 which acts on arm 3 isattached to extension 21 , pre-loading a arm 3 at a distance from theother extension 22 of the base unit. A mechanical path limitation device6 is attached to the second extension 22 of the base unit Thus themaximum movement of arm 3, which can be triggered by the force of spring5 acting on arm 2, which in turn is coupled with arm 3 via the base unitI and the adapter plate 7, is limited.

The mounting positions of arms 2 and 3 on the base unit 1 and theposition of the multi-purpose spring 5 create a lever system, theadvantages of which will be discussed below. The adapter plate 7 holds aheating device 12. This heating device 12 can be designed as required onthe desired application

The base unit 1 is connected to an adjusting element, e.g. a feed bar11. Feed bar 11 is connected to a drive unit 10, e.g. a motor, via aconverter unit 8 and a threaded spindle 9.

The motor 10 as well as the converter unit 8 is attached to one side ofan angular supporting element 15. The other side of the supporting unit15 carries an advancing unit 16 as for example is of the type disclosedin U.S. Pat. No. 5,614,118 to Weber, which issued Mar. 25, 1997. The endof the advancing unit 16 is provided with a component holding device 17which carries a second thermoplastic component 18 to be attached to thecontact surface 24 of a thermoplastic workpiece 13.

The converter unit 8 converts the rotational movement transmitted viathe threaded spindle 9 into a translational motion, at times allowingfor a superimposed rotational movement

When the drive 10 is operated and rotates in the correct direction, thefeed bar 11 performs a combined translational movement (e.g. in FIG. 1 asliding movement in the vertical direction) and swiveling movement (e.g.90°). The base unit 1 is moved from its basic position spaced above theworkpiece 13 into the working position shown in FIG. 1. In this workingposition, the centers of a contact surface 24 on the workpiece 13 andthe center of the heating element 12 are aligned. The converting unit 8is appropriately designed to ensure, as soon as the centers of theheating element and the contact surface are aligned, that the base unit1 performs only a translational movement (vertical downward movement)transmitted by the drive shaft

As the base unit 1 is lowered relative the workpiece, as soon as theheating element 12 touches the elastic contact surface 24, themulti-purpose spring 5 is compressed until arm 3 engages extension 21 ofthe base unit 1, thus triggering a sensor 4 mounted on the end of arm 3.

The spring force of the multi-purpose spring 5 is selected depending onthe elasticity of the contact surface 24. The multi-purpose spring 5should preferably be a spring with adjustable spring force and combinedwith a load sensor or a load cell. In addition to regulating thesensitivity of sensor 4, the multi-purpose spring 5 serves to compensatefor the dead weight of the lever system depending on the position inwhich the entire system is installed.

Triggering of sensor 4 immediately stops the drive 10. The self-lockingeffect of the threaded spindle 9 helps to stabilize the position of thebase unit 1, maintaining it in an accurate spaced relation to thecontact surface 24. Thus it is ensured that the heating element 12always stays in contact with the contact surface 24 independently of theheight tolerance of the contact surface 24.

The force applied by the compressed multi-purpose spring 5 and therestoring force of the contact surface 24 press the heating element intothe contact surface 24. The adjustable mechanical path limitation device6 allows the impression depth of the heating element 12 to be limited toa threshold which can be defined depending on the material of theworkpiece, and in a preferred embodiment used in gas tank manufactureshould amount to approximately 2 mm. The heating element 12 now rests onthe contact surface 24 substantially without exerting any further force,and the heat of the heating element 12 can now penetrate into thesupporting surface 24 practically without displacing any furthermaterial.

The mechanical path limitation device 6 can also be equipped with asensor. In this case, compliance with the defined impression depth uponthe return of the arm 2 into contact with the device 6 can be verifiedand documented.

FIG. 2 shows a modified form of device shown in FIG. 1 used to effectwelding operations while maintaining the workpiece 13 in a deformedstate. In FIG. 2, like reference numerals are used to identify likecomponents. If the elastic return of the contact surface 24 from adeformed state as a result of applied downward force of the heatingelement 12 during the warming phase is not desired forproduction-related reasons, the return of the contact surface 24 to anundeformed configuration may be prevented by the use of a mechanicalpath limitation system 14 mounted on the base unit 1. The mechanicalpath limitation system 14 should be mounted in the vicinity of thecontact surface 24 at a point where the plastic will not be softened andwhere it will be triggered prior to the path limitation system 6.

In operation of either the device shown in FIG. I or the modifiedversion of FIG. 2, during the heating of the contact surface 24, thecontact surface of the second component 18 should for practical reasonsbe simultaneously heated by the end of the heating element 12 oppositethe contact surface 24. This process can be effected by any desiredcomponent holding device 17 and an advancing unit 16 connected thereto,as for example is disclosed in U.S. Pat. No. 5,614,118, and which isconnected with the device of the present invention via a supportingelement 15.

After arrival at the mechanical stop limitation 6 (shown in FIG. 2) anda subsequent waiting period required to let the heat of the heatingelement 12 penetrate the contact surface 24, the drive 10 is nextoperated in the opposite direction to raise the heating element 12 fromthe workpiece 13. It is to be appreciated that the drive 10 must not beactivated before the heating process of the second component 18 iscompleted and the advancing unit 16 has returned to its basic positionretracted above the contact surface 24.

With the activation of the drive 10 in the opposite direction, theheating element 12 is raised from the contact surface 24 (lifted offvertically) and swiveled out of the working zone by a superimposedrotational movement. Then the advancing device 16 lowers and presses themelted portion of the second component 18 onto the melted contactsurface 24 of the workpiece 13.

FIG. 3 shows a side view of the second embodiment of the invention.Identical or similar features in FIG. 3 are allocated the same numberingas a FIG. 1, each number being augmented by a value of 100. For adescription and explanation of the functions of identical or similarcomponents please refer to the description of the first design accordingto FIG. 1.

In the device designed as illustrated in FIG. 3, an angular holdingdevice 130 is mounted at the end of the feed bar 111. The free end ofthis holding device is provided with a holding ring 131. In the centralopening of the holding ring 131, one leg of an angular supporting rod132 slides up and down on a pair of bearing bushes 136. The angular rod132 is provided with a collar 135 which supports a compressible spiralspring 105 which coils around the leg of the angular rod 132 and exertsits pressure against a bearing bush 136. The end of the angular rodopposite from the spring 105 is provided with a stop 133. The free legof the angular rod 132, forming an angle of 90° with the first leg,carries an adapter plate 107 at its free end. The holding ring 131 isprovided with a holding element 134 that suspends the sensor 104 in thevicinity of the free leg of the angular rod 132 in the area where thelatter performs its translational movement.

This second design works similarly to the first design. When the motor110 is activated, the feed bar 111 rotates horizontally through an angleof 90° from the basic position (not shown in the drawing) into theworking position shown in FIG. 3. In this position, the heating device112 is located between and vertically aligned with the contact surface124 and the second component 118. As the motor continues to work, thefeed bar 111 performs a translational movement lowering vertically withthe heating element 112 being pressed against the contact surface 124.As the drive 110 continues to work, the restoring force of the workpiece113 at the contact surface 124 acts against the heating element 112 andcompresses the spring 105. Finally the drive 110 is stopped as thehorizontal arm of the angular rod 132 engages and triggers the sensor104. The position of the heating device 112 is now stabilized due to theself-locking effect of the spindle 109. The workpiece 113 is deformed atthe contact surface 124 due to its contact with element 112 and theelastic force of the compressed spring 105. Due to the force of thecompressed spring 105 and the restoring force of the deformed contactsurface 124, the heating device 112 moves inwardly relative to thecontact surface 124 displacing the material of the workpiece 113 as itbegins to melt. The melting depth can be limited by the adjustable stop133, e.g. to a value of 2 mm. As soon as the stop 133 is in contact withthe bearing bush 136, heat from the heating device 112 penetrates thematerial of the workpiece 113 at the contact surface 124 without furtherforce being exerted or further melted material being displaced.

While the contact surface 124 is heated, the second component 118 ispositioned by the advancing unit 116 on the side of the heating device112 opposite from the contact surface 124 and simultaneously heated. Assoon as a sufficient amount of time for the heating and melting of thecontact surface 124 and the second component 118 has passed, theadvancing unit 116 raises the second component 118, and the drive isreactivated in the opposite direction to lift the heating element 112off the contact surface 124 and to swivel it, at the end of its path oftranslational (e.g. vertical) movement, by an angle of 90° out of theworking position back into the basic position. Then the advancing unit116 alone lowers and presses the still hot and softened surface of thesecond component 118 against the still hot and softened contact surface124 of the workpiece 113 to weld the component 118 to the workpiece 113.After cooling of the plastic weld connection, a durable, strong andexcellent leak-proof connection is achieved.

Both designs illustrated in FIG. 1 and FIG. 3 would allow the workpieceto be elastically or resiliently supported (e.g. on a spring device) andto be moved so as to achieve an initial tension between the heatingelement and the workpiece.

For the designs described above, only the creation of a plastic weldconnection by heating and softening the material of both the workpieceand the component to be attached thereto has been assumed. The expert,however, is aware that the invention disclosed hereunder can also beused for applications where the softening of the workpiece is notachieved by heating but through chemical treatment, glue, and/or sonicwelding either with or without pressing the second component supportedby an elastic device against the workpiece (or vice versa).

While the invention describes and illustrates preferred embodiments ofthe invention, it is to be appreciated that the invention is not solimited. Other modifications and variations will now become apparent toa person skilled in the art. For a definition of the invention,reference may be had to the appended claims.

We claim:
 1. A process for using a device to form a plastic weldconnection between a contact surface of a workpiece that can be deformedby application of a predetermined mechanical force and a component to beconnected thereto, the device including a heating device for softeningthe contact surface of the workpiece, and a heater holding devicemovably supporting the heating device at a desired preloaded positionrelative to the contact surface wherein the heating device applies apreloading force on the workpiece which is generally less than thepredetermined mechanical force, the heating device including a sensor(4,104) activatable to stop movement of the heater holding device whenthe heating device has achieved the preloaded position without measuringof the position of the contact surface, and a repositioning mechanismfor repositioning the heating device relative to the workpiece uponinitial softening of the contact surface by the heating device, theprocess comprising the following steps: positioning the heating devicein initial engagement with the contact surface, moving the heaterholding device relative the workpiece while maintaining engagementbetween the heating device and the contact surface to preload theheating device and activate the sensor, while the heating device softensthe contact surface, repositioning the heating device in relation to theworkpiece by means of the repositioning mechanism, and wherein therepositioning comprises a defined displacement of the heating device inrelation to the contact surface of the workpiece without measuring ofthe position of the contact surface.
 2. The process according to claim1, wherein the heating device is preloaded by moving the heater holdingdevice against the bias of a resilient spring.
 3. The process accordingto claim 1, characterized in that the preloading force is limited to amaximum value.
 4. The process according to claim 1, characterized inthat the preloading force is created by an elastically deformableelement coupled with the heater holding device.
 5. The process accordingto claim 4, characterized in that the limitation of the preloading forceto a maximum value is effected by means of the sensor, and wherein thesensor is triggered upon a predetermined degree of deformation of theelastically deformable element.
 6. The process according to claim 1,characterized in that the component is prepared for connecting to thecontact surface by heating through the heating device simultaneouslywhile the contact surface of the workpiece is prepared by heatingthrough a heating device.
 7. The process according to claim 6,characterized in that a second preloading force acting between thecomponent and the heating device is effected, thus ensuring that theposition of the component is readjusted in relation to the heatingelement while the component is deformed through application of heat bythe heating element.
 8. The process according to claim 1, characterizedin that the repositioning of the heating device is limited to apredetermined distance.
 9. A device for the preparation and formation ofa weld connection between a workpiece that can be deformed by theapplication of a predetermined mechanical force and a component to beconnected thereto, the device including a heating device for thesoftening of a contact surface of the workpiece, and a heater holdingdevice movably supporting the heating device in movement into engagementwith the contact surface, characterized in that the heater holdingdevice movably supports the heating device at a desired positionrelative to the contact surface without measuring of the position of thecontact surface, the device further including a sensor activatable tostop movement of the heating device when the heating device has beenmoved to a preloaded position wherein the heating device applies apreloading force on the workpiece which is generally less than thepredetermined mechanical force, and a repositioning mechanism forrepositioning the heating device relative to the workpiece upon initialsoftening of the contact surface by the heating device.
 10. The deviceaccording to claim 9, further including a biasing element for preloadingthe heating device, the biasing element biasing the heater holdingdevice to readjust the position of the heating device relative to thecontact surface without measuring the position of contact surface. 11.The device according to claim 10, characterized in that the heaterholding device includes a pair of elongated arm members.
 12. The deviceaccording to claim 11, characterized in that the biasing element acts onat least one of the arm members, the heating device being mountedtowards one end of said arm members whereby the biasing element providesleverage forces to assist in the repositioning of the heating device.13. The device according to claim 10, characterized in that thepositioning device comprises two parallel arms which are pivotallyattached to one side of a base unit and on the other side with theheating device for movement substantially in only one direction.
 14. Thedevice according to claim 11, characterized in that repositioning of theheating device is limited to a certain distance by means of a stop whichlimits the movement of the arm member.
 15. The device according to claim9, characterized in that a path limitation device is used to limit therepositioning of the heating device in relation to the workpiece to apredetermined distance.
 16. The device according to claim 15,characterized in that a component holding apparatus for the component isprovided.
 17. The device according to claim 16, characterized in that anadjusting mechanism is used to effect transverse movement of thecomponent holding apparatus for the component in a direction in whichthe heating device can be readjusted.
 18. The device according to claim17, characterized in that the component holding apparatus readjusts theposition of the component in relation to the heating device in the caseof deformation.
 19. The device according to claim 11, characterized by athreaded spindle drive provided for sliding and/or rotational movementof the heater holding device.
 20. The device according to claim 19,characterized in that the threaded spindle drive comprises aself-locking feature.
 21. The device according to claim 9, characterizedin that the heater holding device comprises a pair of substantiallyparallel arm members, a biasing element acts on at least one of a pairof arm members, the heating device being mounted towards one end of saidarm members whereby the biasing element provides leverage forces to saidat least one arm member to assist in the repositioning of the heatingdevice.
 22. The device according to claim 21, characterized in that thebase unit is movable both in a direction along an axis substantiallyparallel to a direction of movement the arm members, as well as radiallyabout said axis.
 23. The device according to claim 9, characterized inthat the heater holding device is mounted on a base unit for linearmovement in one direction.
 24. The device according to claim 9,characterized in that the heater holding device comprises a heatersupporting element which is resiliently biased to a predeterminedposition via an elastically deformable element.